Multiple-stage pump



18, 1966 v. s. LOBANOFF ETAL 3,229,642

MULTIPLE-STAGE PUMP 2 Sheets-Sheet 1 Filed Feb. 28, 1964 INVENTORS F M NM T M m w .0 m LRB mm 9 ATTORNEY 1966 v. s. LOBANOFF ETAL 3,229,642

MULT I PLES TAGE PUMP 2 Sheets-Sheet 2 Filed Feb. 28, 1964 WWW] S R m; M A w L 3 m HAROLD A. STAHL ATTORNEY United States Patent M 3,229,642 MULTIPLE-STAGE PUMP Val S. Lobanotf, Washington, N.J., and Harold A. Stahl, Easton, Pa., assignors to Ingersoll-Rand Company, New York, N.Y., a corporation of New Jersey Filed Feb. 28, 1964, Ser. No. 348,080 7 Claims. (Cl. 103-109) This invention relates to the art of fluid handling machines such as fluid pumps and fluid motors and particularly to plural-stage centrifugal pumps and motors.

One form of multiple-stage centrifugal pump includes a cylindrical outer casing containing a shaft carrying a plurality of impellers and a corresponding number of discharge rings surrounding the impellers for guiding and conducting fluid between the impellers and converting the kinetic energy or velocity of the fluid to potential energy or static pressure. These discharge rings are relatively easy to manufacture since they are separate from the casing. However, since the casing is hollow throughout its length, it expands considerably under high internal pressures. Such expansion is undesirable for various reasons including the fact that it usually causes relatively high rates of leakage between stages which reduces the efficiency of the pump.

Another form of pump uses a casing having the walls of the discharge passages for the impellers formed integrally with the casing. This form of pump casing is much stronger because it contains internal webs which act to prevent the outer walls of the casing from expanding substantially under high pressures. However, this type of pump is very laborious to manufacture with three or more stages because it inherently contains undercut surfaces which must be bored or machined blind with out the machinist being able to see the work or to progressively check it.

The principal object of this invention is to provide a multiple-stage centrifugal pump providing the advantages of the foregoing pumps and eliminating the disadvantages.

Other important objects of this invention include the following: to provide a multiple-stage centrifugal pump or motor having a relatively strong casing which can be manufactured without the need of blind boring or machining; to provide a better, more efficient multiplestage centrifugal pump or motor which can be manufactured less expensively and with less labor; to provide a multiple-stage centrifugal pump or motor having internal passages which can be easily cleaned; to provide a multiple-stage centrifugal pump or motor having a split casing which can be accurately bored and machined without separating the two casing halves each time a surface is checked or a machining tool is changed; to provide a multiple-stage centrifugal pump or motor which is bolted together midway of its length at points substantially near its axis to provide additional strength; and to provide a multiple-stage centrifugal pump or motor which reduces the leakage between stages to a minimum.

In general, these objects are provided by making the pump casing with no more than two stages located midway of its length and having integral walls forming the impeller discharge passages and with the remainder of the stages being formed by separate fluid discharge rings. The integral discharge passage walls reinforce the casing midway of its length and prevent the casing from expanding substantially under internal pressure. Since there are no more than two stages having integral discharge passage walls, these stages can be machined or bored without the need of blind boring methods.

The invention is described in connection with the accompanying drawings wherein:

FIG. 1 is an axial section of a pump embodying this invention;

3 ,229,642 Patented Jan. 18, 1966 FIG. 1A is a fragmentary section showing the left end of the pump of FIG. 1 which is broken away from FIG. 1 along the line 1A1A because of lack of space on a single sheet; and

FIG. 2 is a section of FIG. 1 taken along line 2-2 and drawn on an enlarged scale.

The multiple-stage centrifugal pump shown in FIG. 1 has six stages designated by the reference numbers 1 to 6. The pump includes an outer casing 7 which is formed from longitudinally split halves 8 and 9 which are bolted together by bolts or studs 10, as shown in FIG. 2. The casing 7 includes a fluid inlet 11 at one end and a fluid outlet 12 located about midway of its length. The pump further includes bearings 14 supported at each end of the casing 7 and rotatably carrying an impeller shaft 15 which extends axially through the casing 7 and carries six impellers 16, corresponding to the number of pump stages 1 to 6. The shaft 15 is adapted to be driven by a suitable power means such as an electric motor (not shown) connected to the right end of the shaft, shown in FIG. 1, projecting beyond the bearing 14. All of the foregoing structure is conventional and well known in the pump art.

The two central stages 3 and 6, located about midway of the ends of the shaft 15, are of the volute type wherein an impeller 16 discharges into a volute chamber 18 surrounding each impeller. Each volute chamber 18 is formed in the casing 7 by webs or walls which are integral with the casing. Thus, the chamber 18 for the third stage 3 is formed and located between walls 19 and 20 which are integral with the casing. The chamber 18 for the sixth stage 6 is formed by similar walls 21 and 22. The walls 19 and 22 lie in transverse planes relative to the axis of the casing 7 and serve to reinforce the casing against internal forces which tend to expand or bulge the casing outward.

The two walls 20 and 21 are connected together along their inner peripheries by a tubular section 23 extending axially of and surrounding the shaft 15. The interior of the tubular section 23 is bored or machined and contains a conventional seal ring known as a channel ring 24. The channel ring 24 engages and cooperates with an adjacent wear ring 25 carried by'the shaft 15 to form a seal betwen the third and sixth stages 3 and 6.

Each interior periphery of the walls 19 and 22 also carries a channel ring 26 which is larger in diameter than the channel ring 24 and cooperates with an adjacent impeller to form a seal between stages. Since the channel rings 26 for the walls 19 and 22 are larger than the channel ring 24, the seats for each channel ring 24 and 26 can be bored or machined without resorting to an undercutting operation.

The remaining stages 1, 2, 4 and 5, located outwardly of the stages 3 and 6, are of the diffuser ring type, wherein an impeller discharges into a diffuser ring 28 which is separate from the casing 7 and slides axially into the casing during its assembly. Each diffuser ring 28 is similar for each stage and contains a series of discharge vanes 29 for receiving the high velocity fluid from an impeller 16 and converting the velocity into static pressure which flows into an annular cavity 30 surrounding the ring 28 and located between it and the casing 7. The diffuser ring 28 further contains a group of inlet vanes 31 which direct the fluid radially inwardly from the annular cavity 30 to the inlet of the next succeeding stage. For example, the inlet vanes for the first stage 1 guide fluid from the annular cavity 30 of the first stage 1 to the inlet of the impeller 16 for the second stage 2.

Each end of the casing 7 is closed by an annular closure or end piece 33 and 34 having an annular rib 35 circling its circumference and fitting into an annular internal groove 36 formed in the casing 7. Each of the end pieces axial thrust developed on'the impellers 16 of the first three stages 1 to 3 will counterbalance the thrust of the impellers 16 of the last three stages 4 to 6. As a result, the total axial thrust on the shaft will be relatively small as compared to the thrust which would be developed if all of the stages were sequentially or numerically aligned.

The volute chamber '18 of the sixth stage 6 is connected to the pump outlet 12 for discharging fluid from the pump. This connection is formed in the lower half 9 of the casing 7 during its casting.

It will be noted that the walls and 21 of the third and sixth stages; 3 and *6, are axially spaced and interconnected by horizontal flanges 39 which form extensions of the bolting flanges of the upper and lower halves 8 and 9 of the casing 7. The flanges 39 extend radially and horizontally inwardly to the tubular section 23, surrounding the impeller shaft 1-5, as seen in FIG. 2. Since the flanges 39 extend inwardly near the shaft 1'5, they are bolted together by additional bolts or studs 40 located near the shaft 15 to provide the casing 7 with greatly in creased strength to resist expanding or bulging under internal pressures.

Although only one embodiment of the invention is illustrated and described in detail, it will be understood that the invention is not limited simply to this embodiment, but contemplates other embodiments and variations which utilize the concepts and teachings of this invention. For example, the invention may be useful with fluid motors as well as with the pump described.

Having described our invention, we claim:

'1. A multiple-stage centrifugal fluid machine having at least. three stages comprising:

(a) a casing including integral internal walls located midway of its length and containing a volute dis charge passage for receiving fluid from the periphery of an impeller for at least one stage of the machine;

(b) a plurality of separate rings mounted within said casing and containing discharge passages for. receiv ing fluid from the peripheries of impellers for other stages of the machine;

(c) a shaft extending axially through said casing and carrying multiple impellers corresponding with the stages of said machine; and

(d) removable closures at the opposite ends of said casing to close the interior of the casing.

2. The machine of claim 1 wherein:

(a) said casing is bolted together by bolt means extending transversely through said casing midway of its length near said shaft and within a radial distance from the axis of the shaft which is less than the radius of said separate rings.

3. The machine of claim 1 wherein:

(a) said casing is formed of two separate halves which join each other along longitudinal surfaces and said closures include annular end plates having tongue and groove engagement with said casing halves for preventing said annular end plates from being forced axially apart from the casing by high internal pressures.

4. The machine of claim 1 including:

(a) two center stages having discharge passages formed in integral internal walls in the casing; and

(b) at least one stage at each end of said casing having discharge passages formed in separate rings mounted in said casing.

5. The machine of claim 4 wherein: I

(a) said two center stages are spaced axially apart by walls containing bolts I extending transversely between said center stages and located radially near said shaft.

6. The machine of claim 5 including:

(a) at least two stages at each end of said center stages having discharge passages located in rings separ-ate from said casing.

7. The machine of claim 6 wherein:

(a) the third stage of said machine from one end discharges into a longitudinal passage conveying the fluid to a stage at the other end of said machine whereby the axial thrust developed in three stages of said machine acts in an opposite axial direction to the thrust developed in the other three stages of said machine.

References Cited by the Examiner FOREIGN PATENTS 3/1929 Germany. 12/ 1941 Switzerland.

SAMUEL LEVINE, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

1. A MULTIPLE-STAGE CENTRIFUGAL FLUID MACHINE HAVING AT LEAST THREE STAGES COMPRISING: (A) A CASING INCLUDING INTEGRAL INTERNAL WALLS LOCATED MIDWAY OF ITS LENGTH AND CONTAINING A VOLUTE DISCHARGE PASSAGE FOR RECEIVING FLUID FROM THE PERIPHERY OF AN IMPELLER FOR AT LEAST ONE STAGE OF THE MACHINE; (B) A PLURALITY OF SEPARATE RINGS MOUNTED WITHIN SAID CASING AND CONTAINING DISCHARGE PASSAGES FOR RECEIVING FLUID FROM THE PERIPHERIES OF IMPELLERS FOR OTHER STAGES OF THE MACHINE; 